Minimum visibility seam tape and method of joining substrates using the same

ABSTRACT

A minimum visibility seam tape and method of joining at least two substrates with the tape. The substrates joined typically are sign faces or awnings comprising a composite of thermoplastics and a woven scrim. The seam tape is a woven or nonwoven scrim embedded in or coated with a thermoplastic polymer.

This is as continuation of application Ser. No. 08/099,220 filed Jul.29, 1993 now U.S. Pat. No. 5,906,696 which is a divisional of priorapplication Ser. No. 07/688,648 filed on Apr. 19, 1991 (now U.S. Pat.No. 5,260,113).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a seam tape and method of joining at least twosubstrates with the tape to provide a seam having minimum visibility.The substrates joined are typically sign faces or awnings comprising acomposite of plastics and a woven scrim. The seam tape is a woven ornonwoven scrim embedded in a thermoplastic.

2. Description of the Related Art

Signs, awnings, canopies, fascia and banners (hereinafter referred to assigns) are utilized in applications requiring a strong, flexible,weather-resistant material. These signs are used indoors and outdoorsand are secured to a frame such that the sign is stretched across theframe. The signs often have various color schemes and graphicsemblazoned on them. The colors and graphics can be corporate logos,corporate color patterns, etc. These signs often are rendered visiblefrom a source of backlighting which can either be natural or artificiallight. The construction of the sign substrate generally involves a wovenscrim sandwiched between layers of polymeric materials such asthermoplastics. The scrims are laminated to a thermoplastic such aspolyvinyl chloride, polyester or polyurethane. There are various patentswhich describe such sign materials, including U.S. Pat. Nos. 3,523,856,3,968,275, 4,590,027 and 4,242,380. However, one problem which hasexisted to date is that there is not an adequate material or method toseam these laminates without the seam area being visibly obvious to theviewer. To date, seamed laminates have utilized seam tape with a wovenscrim which was very visible in the seamed laminate, thus resulting in avisible seam.

There are numerous reasons for seaming laminates. Onecommercially-significant reason is to adjoin smaller laminates to createlarge signs. There is often a need for a sign that is larger than thepresently-available sign faces. Therefore, the laminates need to bepieced together to create a larger sign. Another reason to seam is thatoften the scrim has a visible defect produced during the weavingprocess. Other defects include oil, dirt, and insects which may becomepressed into the laminate during the heating process. These defects arecurrently removed from the laminate by removing a strip of material thatcontains the defect. This process reduces the size of the laminate,which leads to the necessity of seaming the laminate to another sectionof laminate.

The seam must be strong such that the seamed laminate can withstandenvironmental conditions, i.e., wind, rain, heat, humidity, etc. Theseam also must have minimal visibility. A seam which is visible ismagnified when the sign is backlit. The seam often shows up as a darkstripe, which is undesirable from an aesthetic point of view.Furthermore, signs often carry logos and colorful graphics in whichvisible seams can often detract significantly from the visual impact ofthe intended message.

To date, the above-identified problems involving the seaming of signshave not been adequately addressed. It has now been discovered that theproblems of seam strength and seam visibility can be minimized throughthe use of a unique seam tape which adjoins sign substrates.

SUMMARY OF THE INVENTION

In accordance with the invention, there is provided a sign faceconstruction and a method of making the sign face construction utilizinga minimally-visible seam tape. The sign face construction is as follows:

At least two sheets of sign face material, each sheet comprising acomposite of layers with a first and third layer comprising a signthermoplastic and a second scrim layer positioned between the first andthird layer, are positioned such that an edge of each sheet is in anabutting relationship, thereby defining an abutting region. A seam tapeextends substantially the length of said abutting region and contactseach of the sheet edges. The seam tape comprises at least a two-layerconstruction of a woven or nonwoven seam scrim having a relatively openfiber pattern and layer of a thermoplastic material coated thereon. Theopen fiber pattern of the seam scrim allows each of the fibers to besubstantially wetted by the thermoplastic material in which the fibersare embedded when the tape is heated under pressure.

One method of using the scrim tape to make a sign face constructioncomprises the steps of:

(a) providing at least two sheets of sign face material, the sheets eachcomprising a composite of layers with a first and third layer of a signthermoplastic material and a second scrim layer positioned between thefirst and third layer;

(b) aligning the two sheets such that an edge of each sheet is in anadjoining position and defines an adjoining region;

(c) positioning the seam tape in the adjoining region such that aportion of the tape contacts each sheet, the tape comprising at least atwo-layer construction of a nonwoven or woven seam scrim having a firstlayer of scrim thermoplastic polymer coated therein, the seam scrimcapable of being substantially wetted out by the scrim thermoplasticpolymer;

(d) heating the adjoining region to a temperature which exceeds themelting temperature of the scrim thermoplastic polymer;

(e) exerting sufficient pressure to the heated region to substantiallywet the seam scrim with said polymer; and

(f) allowing the adjoining region to cool, resulting in a minimallyvisible seam.

The seam tape of the present invention may also be used to securereplacement patches in sign material which have had imperfectionsremoved, as described hereinafter.

DETAILED DESCRIPTION OF THE INVENTION

It has been found that the seam tape of the present invention may beused to join two sections of sign face material to form a strong,integral sign face with a minimally visible seam. The term “minimallyvisible” is meant to denote a seam which is not optically objectionableto the naked eye at normal viewing distances. More specifically,individual scrim fibers are not visible to the naked eye.

This is accomplished in the present invention by (1) selecting scrimmaterials and thermoplastic matrix polymers which have similar indicesof refraction, and are the same color or are transparent, and (2)arranging the scrim fibers in an open relation so that under heat andpressure the thermoplastic matrix polymer will flow around andintimately wet and encapsulate the fibers displacing substantially allof the air in the tape. Due to the similar refractive indices of thescrim fibers and the matrix polymer and the absence of air, the fibersbecome substantially invisible in the matrix, resulting in a relativelyinvisible seam area.

In addition, the seam area can be further rendered unobtrusive bychoosing matrix polymers, scrim materials, and light-absorbing dyes,pigments, etc., so that the apparent color is similar to the sheets tobe joined, and the apparent optical density of the seam region is withinabout ±50% of the region surrounding the seam, preferably within ±25% ofthe apparent optical density of the region surrounding the seam.

The thermoplastic and scrim materials should also be chosen to bechemically compatible with each other and with the sign materials to bejoined. The matrix polymers should adhere well to the sign facematerials and should be relatively stable in the environment in which itwill be used. Many such materials are available and known to thoseskilled in the art as described hereinafter.

The seam tape of the present invention may also be used as a patchmaterial. There are often imperfections in the sign face material whichcan simply be punched out by a die to create an aperture. A replacementpatch of the same sign face material is then cut out and positioned inthe punched-out aperture. A seam tape patch of the present invention isthen cut to a dimension that is bigger than the replacement patch, andplaced over the replacement patch. Heat and pressure are applied to theseam tape region, thereby resulting in a patched region having minimumvisibility.

The substrates which are secured together by the minimally-visible seamtape to form a seam can be any durable and flexible dimensionally-stablematerial to which the seam tape will adhere with the application of heatand pressure. The substrates are often a composite of differentpolymeric materials. Various polyvinyl chloride sheet constructions arecurrently widely used in the sign face industry. A preferred sign facematerial is a substrate comprising a polyester woven scrim embeddedbetween two layers of polyvinyl chloride, commercially available underthe trade designation “PANAFLEX,” available from 3M Company, St. Paul,Minn.

The seaming tape is comprised of a monofilament, loose multifilament,woven, or non-woven scrim. The scrim may be polyester, polyamide,polypropylene, polyethylene, polyurethane, mixes of thermoplastics, orother acceptable scrim materials. Preferably, the scrim is a nonwovenpolyester material.

The scrim can vary in size and denier. The strength and wetability ofthe scrim is the critical feature. The strength should be matched to theapplication's demands, such as indoor, outdoor, etc. The wetability isrelated to the openness of the fibers forming the scrim. If the fibersare tightly packed or twisted, it is difficult for the fibers tosubstantially wet out. This results in trapped air between the fiberswhich absorbs light and creates a dark visible line. Complete wettingresults in a substantially-transparent fiber, thus a minimally-visibleseam. A preferred scrim is a nonwoven polyester having a unit weight of50 gms/m², commercially available from Reemay Inc.

The scrim is coated with, or pressed into a thermoplastic polymer whichhas been cast, extruded, calendered, or other laminating processes. Theindex of refraction of the thermoplastic should be similar to the scrimindex of refraction. Possible thermoplastics include polyester,polyamide, polyimide, polyurethane, polyurea, polypropylene,polyethylene, polycarbonate, and other extrudable thermoplastics. Apreferred thermoplastic is a plastisol of polyvinyl chloride. Acombination of two or more thermoplastics may also be employed.Typically, the thermoplastic is present on the scrim at a weight rangeof about 0.4 gms/cm². The preferred weight range of thermoplasticcoating on the scrim is in the range of about 0.2-1.0 gms/cm². Thethermoplastic may be coated on one side or both sides of the scrim. Analternative embodiment includes the addition of an adhesive on the seamtape. In the preferred embodiment, the scrim is embedded into a gelledthermoplastic polymer and the material is heat-laminated until thethermoplastic has flowed partially through the scrim. The scrim iswetted out and forms an optically-uniform seam in the the final seamedlaminate construction.

The seaming tape may be a variety of widths, but it has been found thata width of about 0.8-3.0 centimeters provides adequate strength to theseamed sign face. Generally, a strip of seaming tape is cut the lengthof the seam. The substrates are positioned in an adjoining relationshipto form an adjoining region, such that there is no gap between thesubstrates. A strip of seam tape is laid over the adjoining region suchthat approximately one half the width of the seam tape is positionedover each substrate. A heat sealer is then applied to the adjoiningregion, applying both heat and pressure to the region which secures theseam tape to each substrate, thus creating a seam. As discussed above,the temperature needs to be above the softening or melting temperatureof the thermoplastic polymer of the seam tape. The pressure appliedshould be sufficient to ensure that the heated thermoplastic flows intothe substrate matrix, thus securing the seaming tape to the substrate.Typical pressures are in the range of about 20 to 1000 KPa.

EXAMPLES

The following examples, in which all parts are by weight unlessotherwise indicated, illustrate various embodiments of theminimally-visible seam tape of the present invention. The examples areexemplary only and are not intended to be limiting.

Samples were prepared and the resulting seam was tested for itsstrength.

Seam Visibility Test

In the following test, sign faces were secured together using the seamtape and method of the present invention and of the prior art. The signfaces were prepared in accordance with the following examples resultingin a seamed construction. The seams were then measured for their opticaldensity and light transmission. Samples of each “PANAFLEX” substrate andthe area where the seaming tape joined the two individual pieces of“PANAFLEX” were measured for optical density (OD). The instruments usedfor these measurements were either a Macbeth Densitometer TR-524 or aTR-927. The procedure used to measure the OD was ANSI Std. ASC PH2.18-1984. A conversion table was used to translate the OD measurementsto percent transmission. The percent transmission for the “PANAFLEX”substrate averages 25.60 for the total number of samples measured. Themeasurement of the seamed areas ranged from a low of 8.128 (the seamcurrently produced in production), up to 31.62% transmission.

Seam Strength Testing

The material to be tested were samples of sign face materials that hadbeen seamed together.

A 2.54 cm wide sample was cut perpendicular to the direction of theseam. The sample was cut such that it was 10 cm in length from each sideof the middle of the seam. This sample was placed into an InstronTensile Strength Tester. The jaw separation used was 5 cm and the samplewas positioned so that the center of the seam was in the middle of thejaw opening. The jaw speed was set at 30.50 cm/minute.

Example 1

Components used in the manufacturing of the seam tape of the presentexamples include a nonwoven nylon scrim, available under the tradedesignation “Cerex Product Type 23” (1 oz./sq.yd.) commerciallyavailable from James River Corporation, a casting liner available underthe trade designation “AW Liner,” commercially available from S.D.Warren Company, and a clear plastisol of polyvinyl chloride, which is ahomopolymer and blending resin of polyvinyl chloride dispersed in amonomeric phthalate plasticizer. The plastisol is available under thetrade designation “DX 2385” and is commercially available fromPlastomeric, Inc. The clear plastisol was coated on the casting liner ata weight of 0.4 gms/cm² and gelled in an oven at a temperature of 95degrees C. The scrim was laminated into this gelled plastisol using ahotcan and pressure. The temperature of the hotcan was 150 degrees C.and the pressure at the nip was 280 KPa. The material was movedcontinuously and the composite was exposed to the pressure andtemperature for a total of 2.5 minutes. The material was then strippedfrom the casting liner and slit into rolls having a width of 1.25centimeter.

The seam tape was then used to seam together two pieces of sign facematerial. The materials used were a sign face product available underthe trade designation “PANAFLEX,” a Teflon tape 5480 commerciallyavailable from 3M Company, and the seaming tape made above. Theequipment used was a flat cutting table, a straight edge, a cuttingtool, and a Vertrod Thermal Impulse Heat Sealer, commercially availablefrom Vertrod Corporation. The two pieces of sign face material are laidon the table face side down, and aligned so that the internal scrim ofthe sign face material matches. One piece was overlapped 10-15 cm overthe other. A straight edge is laid on top of this overlap and a knife isused to cut through the two pieces of sign material. The small excesspieces were removed and the remaining sign face materials were butted upagainst each other. One piece of sign material was laid onto the othersign face so that there was an overlap of approximately 0.8 mm. Themaximum overlap allowed was 0.16 mm. The seam tape was laid onto thisoverlap area so that approximately one half of the tape width was oneach piece of sign face material. This was secured in place with theTeflon tape. The seam tape region was then placed under the opening ofthe heat sealer. The conditions used are 150 degrees C. at a pressure of2.3 Kg in the downward direction, for a dwell time of 45 seconds. Thedwell time includes both heating of the material and cooling the sampledown to 25 degrees C. The Teflon tape is removed and the seam iscompleted.

Example 2

Components used included a polyester multifilament woven scrim availableunder the trade designation “Tetkosilk 14XX,” commercially availablefrom Tetko, Inc., a casting liner “AW Liner,” commercially availablefrom S. D. Warren Company, and a transparent plastisol “DX 2385,”commercially available from Plastomeric, Inc. The procedure used tomanufacture the seaming tape and seam the two pieces of sign facematerial together are exactly the same as described in Example 1.

Example 3

Components used included a polyester multifilament woven scrim availableunder the trade designation of “Tetkosilk 6XX,” commercially availablefrom Tetko, Inc., a casting liner “AW Liner,” commercially availablefrom S. D. Warren Company, and a transparent plastisol “DX 2385,”commercially available from Plastomeric, Inc. The procedure used tomanufacture the seaming tape and seam the two pieces of sign facematerial together are exactly the same as described in Example 1.

Example 4

Components used included a nonwoven polyester scrim available under thetrade designation “Reemay Spunbonded Polyester 2214,” commerciallyavailable from Reemay, Inc., a casting liner available under the tradedesignation “AW Liner,” commercially available from S. D. WarrenCompany, and a transparent plastisol was used to coat both sides of thismaterial. The plastisol is available under the trade designation “DX2385,” commercially available from Plastomeric, Inc. The transparentplastisol was coated on the casting liner at a thickness of 0.3 g/sq.cmand gelled in an oven at a temperature of 95 degrees C. The scrim waslaminated into this gelled plastisol using a hotcan and pressure. Thetemperature of the hotcan was 150 degrees C., and the pressure at thenip was 280 KPa. This composite was then cured in an additional oven ata temperature of 180 degrees C. The material was moving continuously,and the composite was exposed for a total of 2.5 minutes at thetemperature of 180 degrees C. This “First Pass” material was thenstripped from the casting liner and rolled into a separate roll. Thetransparent plastisol was coated on a casting liner at a thickness of0.4 g/sq.cm and gelled in an oven at 95 degrees C. The “First Pass”material was laminated to this gelled plastisol using a hotcan andpressure. The temperature of the hotcan was 170 degrees C. The pressureof lamination was 250 KPa. This material was then cured in an oven at180 degrees C. The material was moving continuously, and the compositewas exposed for a total of 2.5 minutes at that temperature. The lengthof the oven was 30 meters. The material was then stripped from thelasting liner and slit into rolls of 1.25 cm width at some specifiedlength. The procedure used to seam the two pieces of sign face materialtogether was exactly the same as described in Example 1.

Example 5

Components used included a polyester monofilament woven scrim availableunder trade designation “92T,” commercially available from Tetko, Inc.,a casting liner “AW Liner,” commercially available from S. D. Warren anda transparent plastisol designated as “DX 2385,” commercially availablefrom Plastomeric, Inc. The procedure used to manufacture the seamingtape and seam the two pieces of sign face materials together was exactlythe same as described in Example 1.

Example 6

Components used included a polyester multifilament woven scrim availableunder the trade designation “Tetkosilk 6XX,” commercially available fromS. D. Warren, and a transparent plastisol “DX 2385, ” commerciallyavailable from Plastomeric, Inc. The procedure used to manufacture theseaming tape and seam the two pieces of sign face material together wasexactly he same as that described in Example 4.

Example 7

Components used included a polyester multifilament woven scrim availableunder the trade designation “Tetkosilk 6XX,” commercially available fromTetko, Inc., a casting liner available under the trade designation “AWLiner,” commercially available from S. D. Warren Company, and atransparent plastisol available as “DX 2185,” commercially availablefrom Plastomeric, Inc. This transparent plastisol was different informulation from the plastisol used in all other claims of thisinvention. The procedure used to manufacture the seaming tape and seamthe two pieces of sign face materials together was exactly the same asthat described in Example 1.

Example 8

Components used included a nonwoven polyester scrim available under thetrade designation “Reemay Spunbonded Polyester 2014,” commerciallyavailable from Reemay, Inc., a casting liner available under thedesignation “AW Liner,” commercially available from S. D. WarrenCompany, and a transparent plastisol designated “DX 2385,” commerciallyavailable from Plastomeric, Inc. The procedure used to manufacture theseaming tape and seam the two pieces of sign face material together wasexactly the same as that described in Example 1.

Example 9

Components used included a nonwoven polyester scrim available under thetrade designation “Reemay Spunbonded Polyester 2214,” commerciallyavailable from Reemay, Inc., a casting liner designated as “AW Liner,”commercially available from S. D. Warren Company, and a transparentplastisol designated as “DX 2385,” commercially available fromPlastomeric, Inc. The procedure used to manufacture the seaming tape andseam the two pieces of sign face materials together was exactly the sameas described in Example 1.

Comparative Example A

Components used included a polyester multifilament woven scrim,commercially available from Milliken, Inc., casting liner availableunder the designation “AW Liner,” commercially available from S. D.Warren Company, and a transparent plastisol available under the tradedesignation “DX 2385,” commercially available from Plastomeric, Inc.This is an example of a material that is currently available in themarketplace today. The plastisol was coated on both sides of the scrim.The transparent plastisol was coated on a casting liner at a thicknessof 0.4 g/sq.cm, and then it was cured in an oven at a temperature of 165degrees C. As this material exited the oven, it was run under a seriesof IR lights to soften the cured plastisol. The voltage of the lightswere set to give a web temperature of 225 degrees C. This material wasthen laminated to the scrim using a hotcan laminator. The temperature ofthe hotcan was 180 degrees C. and the pressure at the nip was 700 KPa.This material was then stripped from the liner and put into a separateroll. This material is called “First Pass” material. The “Second Pass”material was produced using the same procedure as that described abovefor “First Pass” material, except the roll of “First Pass” product wassubstituted for the scrim. This finished material is stripped from theliner and slit into 1.9 cm rolls of specified length.

In this case, the procedure used to seam two pieces of sign facematerials together was significantly different from that describedabove. Two pieces of sign face was laid onto a flat vacuum table and thetwo pieces of material were overlapped by 10-15 cm. A rotating knife wasused to cut both materials at an angle of 5 degrees. These materials arethen positioned to allow for an overlay of 0.3-0.6 cm. These pieces werethen taped together to keep them from moving. The seaming tape was thenpositioned equally on both sides of the sign face material using aguide, and a series of three heat sealers were used to laminate thematerial together. These heat sealers are a spring-loaded system set toa gap of 0.11 cm. The thickness of the materials prior to using theseheat sealers was 0.2 cm. There was a temperature differential of 225/200degrees C. from the bottom to the top of this heat sealer. This wasfollowed by a set of cooling rolls. The tape was removed, and thiscompleted the seam.

The above seam visibility test and strength test were performed on theabove examples, including the Comparative Example A. The results are asfollows.

TABLE 1 Density of Seam % Trans. % Trans. Seam EXAMPLE PANAFLEX DensityPANAFLEX Seam Strength (lbs.) 1 0.59 0.50 25.70 31.62 56 2 0.60 0.6425.12 22.91 72 3 0.57 0.73 26.02 18.62 102 4 0.59 0.68 25.70 20.89 92 50.60 0.58 25.12 26.30 84 6 0.60 0.74 25.12 18.20 125 7 0.57 0.72 26.0219.05 110 8 0.58 0.71 26.30 19.50 77 9 0.60 0.70 25.12 19.95 65 Cntrl A0.59 1.09 25.70  8.13 122

In the case of seam strength, it is well known that a certain minimumstrength is required to prevent sign damage when exposed to normalenvironmental conditions. Generally, a minimum strength of about 50lbs/linear inch is desired. All examples listed in Table 1 met thisminimum, but there is a very large range. Examples 3, 6, and 7 show theyare equal or very nearly equal in seam strength to the materialcurrently used in production. However, these examples show the lowestpercent transmission of any of the examples. These examples all used the6XX multifilament woven polyester. In comparing the examples with thebest percent transmission, Examples 2, 4, 5, 8, and 9 are very nearlyequal to each other. The seam strength of these materials is less thanthe control, but still exceeds 50 lb. These materials were all madeusing the nonwoven scrim or a very fine woven scrim. Example 1 is aspecial case. It had the lowest strength of any example and the seamtape turned very yellow when the seam was produed. In conclusion, any ofthese examples could be used to produce a minimally visible seam, butseam strength should also be considered.

In view of the foregoing description, it will be apparent that theinvention is not limited to the specific details set forth herein forpurposes of illustration, and that various other modifications areequivalent for the stated and illustrated functions without departingfrom the spirit of the invention and the scope thereof as defined in theappended claims.

What is claimed is:
 1. A method of joining at least two translucent signface substrates with a seam tape to form a seam having a transmissiveoptical density within±about 25% of the transmissive optical density ofthe sign face substrate when the sign face is illuminated from behindthe sign face substrate, said method comprising the steps of: (a)providing at least two sheets of sign face material, such that eachsheet comprises a composite of two layers of a thermoplastic materialand a scrim layer sandwiched between the two layers of thermoplasticmaterial; (b) aligning said two sheets such that an edge of each sheetis in an adjoining position and defines an adjoining region without anygaps between the adjoining sheets of sign face material; (c) positioninga seam tape in said adjoining region such that a portion of said tapesimultaneously overlays and contacts each sheet within the adjoiningregion and extends substantially the length of the adjoining region,said tape comprising a seam scrim substantially embedded in a seamthermoplastic material having an index of refraction similar to thescrim of the seam tape, said seam scrim capable of being substantiallywetted out by said seam thermoplastic material; (d) heating saidadjoining region to a temperature which exceeds the melting temperatureof said seam thermoplastic material; (e) exerting sufficient pressure tosaid heated region to substantially wet out said scrim; and (f) allowingsaid region to cool.
 2. The method of claim 1, wherein the seamthermoplastic material is selected from the group consisting ofpolyester, polyamide, polypropylene, polyethylene, and polyurethane. 3.The method of claim 1, wherein the scrim used for the seam tape is amonofilament, loose multifilament, woven, or non-woven material.
 4. Themethod of claim 1, wherein the two adjoining sheets of sign facematerial within the adjoining region overlap one another.
 5. The methodof claim 1, wherein said seam tape has a second layer of a seamthermoplastic polymer on the opposite side of said seam scrim than saidfirst layer of seam thermoplastic.
 6. The method of claim 1, whereinsaid seam thermoplastic material is gelled prior to incorporating saidseam scrim into said seam thermoplastic material.
 7. A translucent signface construction with a seam comprising: (a) two adjoining sheets ofsign face material, such that each sheet of sign face material comprisestwo layers of thermoplastic and a scrim layer sandwiched between the twolayers of thermoplastic and an edge of one sheet adjoins an edge of theother sheet thereby defining an adjoining region without any gapsbetween the adjoining sheets of sign face material; and (b) a seam tapecomprising a scrim substantially embedded in a thermoplastic materialhaving an index of refraction similar to the scrim of the seam tape,such that the seam tape extends substantially the length of theadjoining region and simultaneously overlays and contacts a portion ofeach adjoining sheet of sign face material within the adjoining region,wherein the seam has a transmissive optical density within±about 25% ofthe transmissive optical density of the sign face material when the signface construction is illuminated from behind the sign face construction.8. The sign face construction according to claim 7, wherein the scrimused for the seam tape is a monofilament, loose multifilament, woven, ornon-woven material.
 9. The sign face construction according to claim 8,wherein the scrim is a non-woven polyester.
 10. The sign faceconstruction according to claim 7, wherein the two adjoining sheets ofsign face material within the adjoining region overlap one another. 11.The sign face construction according to claim 7, wherein the twoadjoining sheets of sign face material within the adjoining region abutone another.